Graminaceae are the major cause of allergy in the Mediterranean area.
Thirteen different types of allergenic proteins, phylogenetically conserved within this family, have been identified in their pollen. For each allergen, the homologous proteins present in the various species constitute a class, inside which high cross-reactivity towards immunoglobulins E (IgE), the antibodies modulating the allergic response, is observed.
Classes 1 and 5 are formed by major allergens, i.e. the most clinically relevant allergens, in that IgEs to the components of these groups are present statistically in more than 80% of subjects allergic to Graminaceae.
Phleum pratense, a Graminacea widely diffused due to its value as fodder, is therefore extremely important from the allergological point of view.
The major allergen Ph1 p 1 of Phleum pratense (identified in GenBank under the accession code X78813) is a protein of 240 amino acids, which in vivo forms one of the components of cell wall (beta-expansin). This allergen has higher than 90% homology to the other class 1 proteins characterized up to now (1). One of the immunochemical properties that Ph1 p 1 shares with the other allergens of the same group is the presence of common epitopes for IgEs (2). As a consequence, the allergen Ph1 p 1 can be used for both the diagnosis and the therapy of the allergies to Graminaceae pollen caused by major allergens of class 1, independently of the species of origin.
The only etiological treatment of allergies is represented by specific hyposensitizing immunotherapy (SIT). This consists in administering increasing doses of the substance which causes the allergy, thus inducing gradual desensitization to said substance in the patient (3).
Immunotherapy may, however, induce even serious systemic effects, which restrict the use thereof (4).
Progresses in SIT, intended to ensure a more effective, safer treatment, include the use of mutagenized recombinant allergens having reduced allergenic activity (reactivity to IgEs) while maintaining unaffected their capability of inducing favourable immunological changes (5).